From: Boris Skorodumov <bskorodo_at_nd.edu>

Date: Wed, 20 Apr 2005 15:29:12 -0500

Date: Wed, 20 Apr 2005 15:29:12 -0500

dear rooters,

imagine, i have tree with var de and e.

i am making 2d histogram t->Draw("de:de+e >>hh") hh.
hh has 422928 Entries.

now i am creating two graphical cuts: cut1 and cut2 which do not have any common points.

later, i am making two 1d histograms with cut1 and cut2

hh->ProjectionX("a",-1,-1,"[cut1]"); a->Integral() gives 6070 hh->ProjectionX("b",-1,-1,"[cut2]"); b->Integral() gives 1967

later i am making other two 1d histograms:

t->Draw("de:de+e >> h1","cut1");

t->Draw("de:de+e >> h2","cut2");

h1->Integral() gives me 5934

h2->Integral() gives me 1936

why that numbers are different from the a and b ?

why the number of entries for a and b which is plotted in the canvas are 422928 but not 6070 and 1967 while for h1 and h2 the number of entries are 5934 and 1936 which is consistent with h1->Integral() and h2->Integral() ?

i was not able to combine cut1 and cut2:

t->Draw("de:de+e >> h3","cut2 || cut1"); h3->Integral() gives me 7870(5934+1936) which is correct.

hh->ProjectionX("rr",-1,-1,"[cut1, cut2]") ignores second cut (cut2). according to http://root.cern.ch/root/html/TH2.html#TH2:ProjectionX that should work.

thank you,

boris.

-- --------------------------------------Received on Wed Apr 20 2005 - 22:34:02 MEST

| Boris Skorodumov, Graduate Student |

| Physics Department |

| University of Notre Dame |

| Indiana 46556, USA |

| WWW: http://www.nd.edu/~bskorodo |

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